Easiest way to do it is the following:
- Open the PDF file in Acrobat.
- Go to Tools - Forms - More Form Options - Export Data.
- Save the form data as an XML file somewhere on your system.
- Open XML the file in a plain-text editor (I recommend Notepad++).
- Let's say you want to replace all the years in the dates from "2013" to "2014". Do a global Search&Replace of "2013-" to "2014-" (I added the dash just to make sure that only date fields are edited).
- Save the XML file (maybe under a new name).
- Go back to the PDF file, and now go to Tools - Forms - More Form Options - Import Data.
- Select the edited XML file and import it.
- Done!







